Dynamic positioning is an important application for marine vehicles that do not have the luxury of anchoring or mooring themselves. Such vehicles are usually large and have arrays of thrusters that allow for controllability in the sway as well as the surge and yaw axes. Most smaller boats however, are underactuated and do not possess control in the sway direction. This makes the control problem significantly more challenging. We address the station keeping problem for a small
autonomous surface vehicle (ASV) with significant windage. The vehicle
is required to hold station at a given position. We describe the design
of a weighted controller that uses wind feed-forward to complement a
Line-Of-Sight guidance controller to achieve satisfactory performance
under slow-varying moderate wind conditions. We test the control
system in simulation and in field trials with a twin-propeller
ASV. Experiments show that the controller works very well in moderate
wind conditions allowing the ASV to keep station with a position error
of approximately one vehicle length.